Both experienced growers and newcomers might encounter unforeseen situations with these crops. Whether you’re cultivating your plants in coco coir, soil, or hydroponics, you’ll notice various blemishes on the cannabis leaves.

One of the most prevalent issues when it comes to cannabis cultivation is the appearance of yellow stains on the leaves. In this resource, you’ll discover everything you need to understand their source and how to keep yellow cannabis leaves from showing up!

Why do cannabis leaves turn yellow?

To understand how to address yellowing leaves on our marijuana plants, we need to first identify the potential causes. Some factors include:

pH Levels

One of the primary reasons for leaves turning yellow is the improper pH levels of the nutrient solution. When you’re growing in soil, aim to keep pH levels ideally between 6 and 7. If you’re using coco coir or hydroponics, you can let them range from 5.5 to 6.5. If you notice yellowing leaves, it may indicate a pH imbalance.

When pH levels are too low or too high, they can hinder the plant’s ability to absorb essential elements from the provided solution. This disruption can lead to a blockage in the uptake of both macro and micronutrients.

To address this issue, it’s advisable to utilize a pH meter and select cannabis fertilizers with a broader pH range, encompassing all the necessary microelements. Root washing and restarting fertilization with a more suitable solution for the growing medium can be beneficial. However, the key is to create the most optimal environment for the plants.

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Temperature and Humidity

Inappropriate temperature and humidity levels can also cause the leaves of your plants or strains to turn yellow. The ideal temperature range for growing cannabis is between 10-28°C (50-82.4°F).

To prevent yellowing due to temperature and humidity issues, you should adjust the temperature as needed. This may involve providing more light in the grow room or installing additional input-output fans in the grow tent. When growing outdoors, you can use structures to create shade or act as a greenhouse.

Incorrect Irrigation

This is another common issue. Overwatering or underwatering can also result in yellowing cannabis leaves. Some symptoms of improper irrigation include:

• Plant drooping
• Excessive watering causes edema disorder.
• Thin and pale leaves due to insufficient watering.
• Root rot caused by excessive watering: You can determine whether you’re dealing with excessive or insufficient irrigation by checking the moisture level of the substrate. To address this, simply adjust your watering, either by reducing it or providing more water to the plant, as needed.

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Fertilizer Management: lack of nutrients… or the opposite!

Inadequate nutrient levels can lead to nutritional deficiencies that disrupt cannabis growth, as they prevent the plants from carrying out their essential functions. On the other hand, over-fertilizing your plants can lead to nutrient burn and subsequent leaf yellowing. It’s important to remember that nitrogen, phosphorus, and potassium (NPK) are essential nutrients for plants.

Common nutrient-related problems include:

• Nitrogen deficiency symptoms, start with yellowing leaf edges and then spread across the entire leaf. However, if you notice overly bright leaves during the growth stage, it may be a result of over-fertilization.
• A lack of potassium, an essential mineral for photosynthesis and stomatal function, can cause your leaves to turn yellow when there’s a deficiency of this compound.

To avoid these issues, it’s crucial to manage nutrient levels and understand the benefits that nutrients offer to each plant.

Fungi

Fungal diseases and infections, such as septoria, can pose significant threats to your plants. To spot these issues, a simple leaf inspection is often sufficient, as pests tend to congregate on the leaves, potentially leading to yellowing. The septoria infection, in particular, can be harmful at any stage of the plant’s life.

To address these problems, you can use pesticides or introduce beneficial insects that combat pests without harming the plant. When dealing with septoria, it’s crucial to remove infected foliage and regularly clean your tools after each use.

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Tips for Preventing Cannabis Leaves from Turning Yellow:

Here are some useful tips:

• Choose your cultivation method based on your strain’s resistance, whether you’re growing indoors or outdoors.
• Adjust and fine-tune your irrigation practices.
• Make sure your plants don’t get too much heat, and adjust your grow lights as needed
• Keep an eye on temperature and humidity levels, aiming for a range of 15-29 °C (59-84.2 °F) during the daytime.
• Avoid placing your plants on cold surfaces, as freezing roots can reduce cold resistance.
• Provide the appropriate nutrients to your plants.
• Check your cannabis leaves daily to spot any signs of yellowing. If you detect an issue, investigate possible nutrient deficiencies or excesses.
• In the case of a deficiency, provide the necessary substance to the plant. If there’s an excess, perform a root wash and temporarily discontinue the use of fertilizers. When you resume fertilization, adhere to a proper schedule.

It’s worth noting that yellow leaves are a normal occurrence in cannabis plants during the late flowering stage, as they naturally shed older leaves to conserve energy. The same applies when conducting a root wash. Therefore, it’s important to consider all the factors mentioned above to prevent these problems!